Rotary substrate holder assembly

ABSTRACT

A rotary substrate holder assembly comprising a pair of hemispherical substrate supporting members is provided to hold and retain a plurality of substrates during film deposition, ion implantation and other material treatment processing. The substrate supporting members or holders are supported within a bell jar by a pair of horizontally extending drive shafts. Holder support shafts and gear means are provided to operate in conjunction with the drive shafts to rotate each of the holders about their respective axes, as well as about an axis orthogonal to their respective axes. Single and dual motor drives and various gear ratios are provided for driving the holders with various ratios of rotational and revolutionary motion therefore available as is required by a particular application. In addition, means are provided to separately control rotational and revolutionary motion imparted to the holders for use in step and repeat processes and the use of flat as well as dish-shaped substrate holders.

United States Patent [1 1 Slabaugh [451 July 31, 1973 1 ROTARY SUBSTRATE HOLDER ASSEMBLY [75] Inventor: Edward J. Slabaugh, San Jose, Calif. [73] Assignee:- Ion Equipment Corp., Santa Clara,

Calif.

[22] Filed: July 26, 1971 [21] Appl. No.: 165,940

[52] U.S. C1 118/500, 74/660, 118/48, 118/53 [51] Int. Cl. 1305c 11/14 [58] Field of Search ..1 18/52-57, 48-495, 500403; 117/101, 109; 74/660 [56] References UNITED STATES PATENTS 2,824,029 2/1958 Zinty 118/53 UX 2,997,979 8/1961 Tasara 118/49 3,046,157 7/1962 Nyman 118/53 UX 3,105,776 10/1963 Weyhmueller 118/416 X 3,131,917 5/1964 Gessner et a1. 118/59 X 3,297,475 1/1967 Flacche 118/53 X 3,583,363 6/1971 Shrader 118/500 3,656,453 4/1972 Tousirnis 118/48 Primary Examiner-Morris Kaplan Attorney-Warren M. Becker'et a1.

[57] ABSTRACT A rotary substrate holder assembly comprising a pair of hemispherical substrate supporting members is provided to hold and retain a plurality of substrates during film deposition, ion implantation and other material treatment processing. The substrate supporting members or holders are supported within a bell jar by a pair of horizontally extending drive shafts. Holder support shafts and gear means are provided to operate in conjunction with the drive shafts to rotate each of the holders about their respective axes, as well as about an axis orthogonal to their respective axes. Single and dual motor drives and various gear ratios are provided for driving the holders with various ratios of rotational and revolutionary motion therefore available as is required by a particular application. In addition, means are provided to separately control rotational and revolutionary motion imparted to the holders for use in step and repeat processes and the use of flat as well as dish-shaped substrate holders.

10 Claims, 7 Drawing Figures PATENTEIJ JUL 3 1 I975 3. 749 .058

sum 1 [IF 3 INVENTOR. EDWARD J. SLABAUGH ATTORNEYS PAIENIE JUL 3 1 am sum 2 or 3 F's 5 EDWAR FgL E AUGH BY fll ATTORNEYS PATENTEDJULIB 1 ma SHEEI 3 0F 3 INVENTOR. EDWARD J. SLABAUGH BY ATTORNEYS 1 ROTARY SUBSTRATE HOLDER ASSEMBLY BACKGROUND OF THE INVENTION and vapor deposition processes, uniformity of film thickness, substrate heating, highthroughput, simplicity, flexibility and cleanliness of equipment are principal considerations in producing commercially acceptable products at low cost.

Inthese and other applications, such as ion implantation used in doping'semiconductor materials, a high capacity rotary substrate holder capable also of step and repeat operation isfrequently required.

A high capacity fixture to hold substrates with all of the above-mentionedfeatures. and with the capacity to rotate as well as revolve the substrate holders in either a continuous or a. step and repeat process is therefore very important to. an overall manufacturing process.

SUMMARY OF THE INVENTION In accordance withthe preferred embodiment of the The hemispheres and'gearassembly aresuppo'rted in a bell: jar and drivenby the. powersourcethroughshafts which pass into the bell jar through rotary feedthroughs.

The provision for hemispherically shaped substrate holders provides for increased wafer capacity by in-- creasing the number of wafers or substrates that can be processed eachcycle of operation.

Improved substrate heating is available because heating can be donefrominside thesphere. This reduces the required heating time and increases'heatinguniformity because of greatly increased geometrical efficiency. In addition, by containing the radiant. heat within the sphere, there is much less heating of other surfaces in the system, including the bell jar itself. Therefore, outgassing of such surfaces will be correspondingly decreased, and contamination of the substrates by evolved gases will be reduced. The reduction in evolvedgases provides an immediate increase in the quality of the wafer circuits; i.e., the quality of theend product.

Improved evaporationshielding is also obtained with hemispherical substrate holders. With all wafers in place, the double-dome is optically dense tothe evaporation stream. This eliminates the usualcomplex shielding required to contain the evaporation, and provides a cleaner system, with smaller surface area and therefore lower outgassingand less contamination of wafer surfaces. Periodic cleaning of the system to remove excess evaporant is accomplished simply by cleaning the hemispheres. Down time is, therefore, reduced.

In one-embodiment ofthe present invention a differential gear assembly utilizing a single motor is provided to simultaneously rotate the holders about a first axis as well as aboutan axis orthogonal to the first axis. In

another embodiment, two motors are used to providean infinitely variable ratio between the rotational and revolutionary motion imparted to the holders. In still another embodiment, the features of the last named embodiment with a modified gear assembly are available for step and repeat processing provided predetermined gear ratios are used.

In addition, flat as well as dish-shaped substrate holders may be substituted for the preferred hemispherical holders as is required in a particular application.

These and other features and advantages of the present invention will be apparent in the following detailed description describing the accompanying drawings.

DESCRIPTION OFV'IHE DRAWINGS FIG. 1 is an elevation view of the present invention.

FIG. 2 is a partial cross-sectional view of a gear assembly of the present invention.

FIG. 3 is a partial cross-sectional view of an alternative gear assembly of the present invention.

FIG. 4 is an elevation view of the holders 4, 5 of FIG. 1 as used in a step and repeat process.

FIG. 5 is an elevation view of the present invention using flat substrate holders.

FIG. 6 is an elevation view of the present invention using disk shaped substrate holders.

FIG. 7 is a side view of FIG. 6.

DETAILED DESCRIPTION Referring to FIG. 1, there is provided in accordance withthe present'invention a rotary substrate holder assembly'l which is mounted in a bell jar 2 fitted to a base plate 3. Bell jar 2 is typically 18 inches in diameter and A constructed entirely of stainless steel though other materials and sizes may be used in whole or in part-as is required by a particular application. Vacuum equipment not shown is provided to evacuate bell jar 2in a conventional manner.

Rotary substrate holder assembly 1 comprises a pair of substrate holders 4, 5. Each of holders 4, 5 is provided with conventional means not shown to retain a plurality of substrates 6. Substrate holders 4, 5 are supported by and coupled to a gear assembly 10 by means of a pair of dome support shafts 11, 12. A second pair of shafts, drive shafts, l3, 14 are mounted orthogonal to shafts I1, 12 and extend externally of bell jar 2 through a pair of rotary vacuum feedthroughs 15, 16. Shaft 13 is coupled'to a motor 20 and shaft 14 is coupled to a motor 21. In certain applications, as will be described in more detail below, either motor 20 or 21 may be omitted and theshaft associated therewith held stationary relative to the other shaft.

In a typical application, rotary substrate holder as sembly 1 is mounted above an evaporation source 25. Source 25 is provided with an evaporation shield 26. Source 25 is typically heated to a high temperature by means not shown to evaporate any one or a combination of materials with which it is desired to coat substrates 6. Evaporation shield 26 serves to confine the evaporating material within the dashed lines 27 to prevent loss of evaporating materials and undesirable coating of the interior of the bell jar 2.

To provide a uniform and high quality film on each of substrates 6, it is necessary to rotate substrates 6 through the evaporation stream. It is found that this uniformity and quality of coating is achieved by rotating substrate holders 4, 5 about an axis coaxial with shafts ll, 12 as well as about an axis coaxial with shafts 13, 14. This rotational and revolutionary motion of substrate holders 4, 5 is provided by gear assembly 10.

Referring to FIG. 2, shafts 11, 12, 13, 14 are terminated by bevel gears 31, 32 33 and 34, respectively. A plurality of bearing sets 41-44 maintain shafts 13-14 centrally located within a gear housing 45 provided to contain gears 31-34.

In operation, motor drives shaft 13 in a clockwise direction as shown by the arrow. By holding shaft 14 stationary relative to shaft 13, the interaction of bevel gears 31-34 is such as to impart counter-rotating motion to substrate holders 4, 5. At the same time, gears 31-34 cause shafts 11, 12 and hence substrate holders 4, 5 to revolve about an axis orthogonal to their respective axis of rotation. The orthogonal axis is typically a horizontal axis coaxial with shafts 13, 14. As previously indicated when substrate holder assembly 1 is used in this manner, motor 20 or 21 may be omitted and other means provided for holding its associated shaft stationary.

In certain other applications, however, it is desired to rotate substrate holders 4, 5 about a first axis while controlling independently the rate of revolution of substrate holders 4, 5 about the axis orthogonal thereto. In these cases both motors 20, 21 are used in conjunction with any compatible ratio of gears to achieve an infinitely variable ratio between the rotational and revolutionary motion imparted to the holders. It is noted, however, that in any case both rotational and revolutionary motion is present.

To provide independent and selective control over the rotation and revolutionary motion of substrate holders 4, 5, there is further provided as shown in FIG. 3 an alternative gear assembly 50. When using gear assembly 50, substrate holders 4, 5 are coupled to the opposite ends of a single shaft member 51. In a manner similar to that described with respect to FIG. 2, shaft 13 coupled to motor 20 is terminated by a beveled gear 52 which is provided to engage a gear member 53 fixedly attached to shaft 51. An idler gear 54 is engaged by gear member 53 but is permitted to rotate freely about shaft 14 on a bearing set 55. A second idler gear 56 is provided to engage idler gear 54 and beveled gear 52 and rotate freely about shaft 51 on a second bearing set 57. Though serving no driving function, idler gears 54 and 56 serve to maintain mechanical alignment of each of shafts 13, 14 and 51.

Shaft 14 is coupled to shaft 51 by means of a bearing housing flange 60. Housing flange 60 is provided with a pair of bearing members 61, 62 located on opposite sides of gears 53, 56. Shaft 51 passes through bearing members 61, 62 and is provided to freely rotate therein.

Upon the application of clockwise torque to shaft 13, shaft 51 and hence holders 4, 5 are caused to rotate counterclockwise as shown by the arrows. With an application of torque to shaft 14 by motor 21 revolutionary motion about the axis coaxial with shaft 14 may be imparted to shaft 51 and holders 4, 5 through flange member 60. By separately controlling the rotational and revolutionary motion imparted to substrate holders 4, 5, it is possible to obtain not only an infinitely variable ratio between the rate of rotation and rate of revolution of substrate holders 4, 5 as described with respect to the dual motor embodiment using gear assembly 10, but is also possible to obtain the control necessary for use of the invention in a step and repeat process provided a preselected gear ratio is used.

In certain applications, such as the aforementioned ion implantation of semi-conductor devices, it is necessary to expose each device individually to an ion beam. This involves essentially a step and repeat process which is possible with the rotary substrate holders 24,

of FIG. 4 using the gear assembly 50 of FIG. 3.

When so used the evaporation source 25 of FIG. 1 is replaced by an ion beam source. The ion beam is orientated 90 to the horizontal axis in the place of revolution of shaft 51 of gear assembly 50 and directed along a line which passes through the true center of the sphere formed by holders 4, 5. If shaft 13 is held stationary while shaft 14 is revolved, the ion beam will describe an epicycloidal pattern on the surface of the sphere.

Referring to FIG. 4, if substates 6 are placed about the sphere in the epicycloidal pattern, their position would appear as describing diagonal rows, 1, 2, 3, 4, etc., about the surface of the sphere formed by holders 4, 5. With such an arrangement, each substrate 6 is caused to intercept the ion beam. The substrates 6 are then individually implanted and then indexed to the next substrate by merely revolving shaft 14. The degree of revolution of shaft 14 is controlled by a suitable conventional microswitch cam assembly not shown in a conventional manner. When each of substrates 6 in Row 1 is suitably treated, indexing to the next row, row 2, row 3, etc., is done by holding shaft 14 stationary and rotating shaft 13 to the next row. Again, the amount of rotation of shaft 13 is controlled by a conventional microswitch cam assembly in a well-known manner.

In practice and in contrast to the selection of gear ratios available for use of the invention for film deposition it has been found that in the illustrated step and repeat process a 2 to 1 ratio between gears 52 and 53 of gear assembly 50 is preferable to provide for a suitable or maximum packing density of substrates 6 about holders 24, 25, of approximately 108 1% inch substrates on a 15-inch diameter sphere. If the ratio is increased, the position of substrates 6 must be spread apart. If the ratio is reduced, the required positions for substrates 6 tend to overlap.

The availability of independent control over the rotational and revoluntionary motion of the substrate holders further allows the use of a pair of flat substrate holders 70, 71 as shown in elevation in FIG. 5 or alternatively a plurality of dish-shaped substrate holders 72-75 as illustrated in cross-section FIGS. 6, 7.

As shown in FIG. 5, with the exception of flat substrate holders 70, 71, the apparatus of FIG. 5 is identical to that of FIG. 1 and 3. To permit vapor deposition of substrates 6 supported by substrate holder 71, both substrate holders 70, 71 are rotated by motor 20 through gear box 50. After a predetermined length of time determined by the thickness and uniformity of the film desired on the substrates. motor 21 is energized to index substrate holder into the position formerly held by substrate holder 71. Motor 21 is then deenergized and motor 20 is again energized to repeat the coating process.

Referring to FIGS. 6 and 7, a modified gear assembly 82 comprising the features of gear assembly 50 is provided with shafts 11, 12 supporting a part of dishshaped substrate holders 72, 74 and a pair of additional shafts 80, 81 for supporting a pair of dish-shaped substrate holders 73, 75 disposed orthogonal to both shafts l l, 12 and 13, 14. Shafts 80, 81 are each terminated by a bevel gear in the manner of shafts l1, 12 shown in FIG. 2. The bevel gears on shafts 80, 81 engage bevel gears 52, 53 on shafts 13, 51 and idler gears 52, 56. As described with respect to the holders of FIG. 5, when the substrates on one of substrate holders 72-75 have been coated, motor 21 is energized to index the next substrate holder into position above the evaporation source.

While the invention has been described with respect to its use in a vapor deposition process and a step and repeat process encountered in ion implantation of semi-conductor devices, it will be appreciated that the invention is also useful in other material treatment processes such as sputtering provided the equipment is modified to incorporate the convention electrical and cooling equipment therein required.

I claim:

1. A rotary substrate holder assembly comprising: substrate support means; means for rotating said substrate supporting means about a first axis; means for revolvin g said substrate supporting means about a second axis orthogonal to said first axis; said substrate supporting means comprising a first substrate holder and a second substrate holder; said means for rotating said substrate supporting means about said first axis comprising a gear assembly; a first shaft means coaxial with said first axis coupled to said gear assembly for supporting said first and said second substrate holders; a second shaft means rotatably coupled orthogonally to said first shaft means through said gear assembly; means for applying torque to said second shaft means for providing by means of said gear assembly said rotation of said first and said second substrate holders about said first axis; and said means for revolving said substrate supporting means about said second axis orthogonal to said first axis comprising a third shaft means coaxial with said second axis coupled to said first shaft means; and means coupled to said third shaft means for providing said revolution of said first and said second substrate holders about said second axis.

2. A rotary substrate holder assembly according to claim 1 wherein said means coupled to said third shaft means for providing said revolution of said first and said second substrate holders about said second axis comprises: means coupling said third means to said first shaft means through said gear assembly; and means for holding said third shaft means stationary with respect to said second shaft means whereby said first and said second substrate holders counter-rotate about said first axis while simultaneously revolving about said second axis when torque is applied to said second shaft means.

3. A rotary substrate holder assembly according to claim 1 wherein said first shaft means coaxial with said first axis coupled to said first and said second substrate holder and said gear assembly comprises a single continuous shaft, said means coupled to said third shaft means for providing said revolution of said first and said second substrate holders about said second axis comprises means for applying a torque to said third shaft; a flange member fixed to said third shaft adjacent to said first shaft, said rotary substrate holder assembly further comprising a bearing housing adapted to receive said first shaft and fixedly attached to said flange member for permitting said rotation of said first and said second substrate holders about said first axis when torque is applied to said second shaft means and said revolution of said first and said second substrate holders about said second axis where torque is applied to said third shaft means.

4. A rotary substrate holder assembly according to claim 3 wherein said first andsaid second substrate holders comprise a first and a second hemisphere, each of said hemispheres being further provided with a plurality of means for retaining a plurality of substrates on the surface thereof.

5. A rotary substrate holder assembly according to claim 3 wherein said first and said second substrate holders comprise a first and a second hemisphere, each of said hemispheres being further provided with a plurality of means for retaining a plurality of substrates on the surface thereof.

6. A rotary substrate holder assembly comprising a first substrate holder; a second substrate holder; a gear assembly; a first shaft member for coupling said first substrate holder to said gear assembly for rotatably supporting said first substrate holder; at second shaft member for coupling said second substrate holder to said gear assembly for rotatably supporting said second substrate holder; a third shaft member disposed orthogonally to said first and said second shaft member; a fourth shaft member disposed orthogonally to said first and said second shaft member, said gear assembly comprising means for rotatably coupling said third and said fourth shaft members to said first and said second shaft members; means for applying torque to said third shaft member for rotating said first substrate holder about an axis coaxial with said first shaft member and said second substrate holder about an axis coaxial with said second shaft member; and means coupled to said fourth shaft member for applying torque to said fourth shaft member for selectively revolving said first and said second substrate holders about an axis coaxial with said third and said fourth shaft members.

7. A rotary substrate holder assembly according to claim 6 wherein said gear assembly comprises first, second, third and fourth gears terminating said first, second, third and fourth shaft members respectively, and said means coupled to said fourth shaft member comprises means for holding said fourth shaft member stationary relative to said third shaft member whereby said first, second third and fourth gears rotatably engage to rotate and revolve said first and said second substrate holders about said first and said second axis simultaneously.

8. A rotary substrate holder assembly according to claim 7 wherein said first and said second substrate holders are hemispherically shaped.

9. A rotary substrate holder assembly according to claim 6 wherein said gear assembly comprises first, second, third and fourth gears terminating said first, second, third and fourth shaft members respectively, said means for applying torque to said third shaft member comprises a first motor means and said means coupled to said fourth shaft member comprises a second motor means.

10. A rotary substrate holder assembly according to claim 6 wherein said first and said second shaft members comprise a single shaft coupled to said first and said second substrate holders; said gear assembly comprising a gear housing; means fixedly coupling said fourth shaft member to said housing; and means within said housing for receiving said single shaft for permitting said single shaft to rotate freely therein.

1! i i i 

1. A rotary substrate holder assembly comprising: substrate support means; means for rotating said substrate supporting means about a first axis; means for revolving said substrate supporting means about a second axis orthogonal to said first axis; said substrate supporting means comprising a first substrate holder and a second substrate holder; said means for rotating said substrate supporting means about said first axis comprising a gear assembly; a first shaft means coaxial with said first axis coupled to said gear assembly for supporting said first and said second substrate holders; a second shaft means rotatably coupled orthogonally to said first shaft means through said gear assembly; means for applying torque to said second shaft means for providing by means of said gear assembly said rotation of said first and said second substrate holders about said first axis; and said means for revolving said substrate supporting means about said second axis orthogonal to said first axis comprising a third shaft means coaxial with said second axis coupled to said first shaft means; and means coupled to said third shaft means for providing said revolution of said first and said second substrate holders about said second axis.
 2. A rotary substrate holder assembly according to claim 1 wherein said means coupled to said third shaft means for providing said revolution of said first and said second substrate holders about said second axis comprises: means coupling said third means to said first shaft means through said gear assembly; and means for holding said third shaft means stationary with respect to said second shaft means whereby said first and said second substrate holders counter-rotate about said first axis while simultaneously revolving about said second axis when torque is applied to said second shaft means.
 3. A rotary substrate holder assembly according to claim 1 wherein said first shaft means coaxial with said first axis coupled to said first and said second substrate holder and said gear assembly comprises a single continuous shaft, said means coupled to said third shaft means for providing said revolution of said first and said second substrate holders about said second axis comprises means for applying a torque to said third shaft; a flange member fixed to said third shaft adjacent to said first shaft, said rotary substrate holder assembly further comprising a bearing housing adapted to receive said first shaft and fixedly attached to said flange member for permitting said rotation of said first and said second substrate holders about said first axis when torque is applied to said second shaft means and said revolution of said first and said second substrate holders about said second axis where torque is applied to said third shaft means.
 4. A rotary substrate holder assembly according to claim 3 wherein said first and said second substrate holders comprise a first and a second hemisphere, each of said hemispheres being further provided with a plurality of means for retaining a plurality of substrates on the surface thereof.
 5. A rotary substrate holder assembly according to claim 3 wherein said first and said second substrate holders comprise a first and a second hemisphere, each of said hemispheres being further provided with a plurality of means for retaining a plurality of substrates on the surface thereof.
 6. A rotary substrate holder assembly comprising a first substrate holder; a second substrate holder; a gear assembly; a first shaft member for coupling said first substrate holder to said gear assembly for rotatably supporting said first substrate holder; a second shaft member for coupling said second substrate holder to said gear assembly for rotatably supPorting said second substrate holder; a third shaft member disposed orthogonally to said first and said second shaft member; a fourth shaft member disposed orthogonally to said first and said second shaft member, said gear assembly comprising means for rotatably coupling said third and said fourth shaft members to said first and said second shaft members; means for applying torque to said third shaft member for rotating said first substrate holder about an axis coaxial with said first shaft member and said second substrate holder about an axis coaxial with said second shaft member; and means coupled to said fourth shaft member for applying torque to said fourth shaft member for selectively revolving said first and said second substrate holders about an axis coaxial with said third and said fourth shaft members.
 7. A rotary substrate holder assembly according to claim 6 wherein said gear assembly comprises first, second, third and fourth gears terminating said first, second, third and fourth shaft members respectively, and said means coupled to said fourth shaft member comprises means for holding said fourth shaft member stationary relative to said third shaft member whereby said first, second third and fourth gears rotatably engage to rotate and revolve said first and said second substrate holders about said first and said second axis simultaneously.
 8. A rotary substrate holder assembly according to claim 7 wherein said first and said second substrate holders are hemispherically shaped.
 9. A rotary substrate holder assembly according to claim 6 wherein said gear assembly comprises first, second, third and fourth gears terminating said first, second, third and fourth shaft members respectively, said means for applying torque to said third shaft member comprises a first motor means and said means coupled to said fourth shaft member comprises a second motor means.
 10. A rotary substrate holder assembly according to claim 6 wherein said first and said second shaft members comprise a single shaft coupled to said first and said second substrate holders; said gear assembly comprising a gear housing; means fixedly coupling said fourth shaft member to said housing; and means within said housing for receiving said single shaft for permitting said single shaft to rotate freely therein. 